Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $206.75   3.541%   $214.071   $214.07   $214.05   $214.10  
  Purchase #2 $122.43   8.499%   $132.8353   $132.84   $132.85   $132.80  
  Purchase #3 $151.93   8.273%   $164.4992   $164.50   $164.50   $164.50  
  Purchase #4 $199.49   8.616%   $216.6781   $216.68   $216.70   $216.70  
  Purchase #5 $189.25   13.543%   $214.8801   $214.88   $214.90   $214.90  
  Purchase #6 $132.72   9.553%   $145.3987   $145.40   $145.40   $145.40  
  Purchase #7 $60.67   5.589%   $64.0608   $64.06   $64.05   $64.10  
  7 purchase totals = $1,063.24       $1,152.4232   $1,152.43   $1,152.45   $1,152.50